TAMPA, Fla. -- Once Steven Stamkos scored, there was no stopping him from doing it again.

The NHL goals leader scored twice to reach 50 in a season for the second time, and the Tampa Bay Lightning jumped out to a big early lead before coasting to a 6-1 victory over the Boston Bruins on Tuesday night.

The 22-year-old Stamkos, who moved into a tie for the league scoring lead with Evgeni Malkin with 84 points, also scored his 49th and 50th goals in the same game two seasons ago.

"It was definitely in the back of my mind. It was nice last time I did it to get to 49 and 50 in one game," said Stamkos, the first pick in the 2008 draft. "That was definitely running through my mind."

Tampa Bay scored three times in the first five minutes and made it easy for rookie goalie Dustin Tokarski, who earned his first NHL victory.

Tom Pyatt, Nate Thompson and Ryan Shannon led the surge that ruined Marty Turco's first start as Boston's backup goalie. The defending Stanley Cup champions have lost three straight for the first time since late October and were limited to two shots in the opening period, 34 overall.

Stamkos scored his 49th goal in the second period and added his NHL-best 50th at 11:43 of the third. He is the sixth player in league history to score 50 goals twice before age 23, and Lightning Guy Boucher feels he is capable of more.

The Bruins signed Turco on March 5 as a backup for No. 1 goalie Tim Thomas after Tuukka Rask sustained a lower abdomen-groin strain that could sideline him four to six weeks. The 36-year-old Turco played 40 minutes in relief during a 5-2 loss on Sunday at Pittsburgh, becoming the first goalie other than Thomas or Rask to play for Boston in nearly three years.

Thomas replaced Turco after Shannon's goal made it 3-0 just 4:31 in, but he didn't fare much better. Bruins coach Claude Julien went back to Turco after Thomas yielded a goal to Victor Hedman late in the first period, then another to Stamkos early in the second.

The Bruins didn't make either goalie available for interviews after the game.

Boston has lost three consecutive games for the first time since falling to San Jose and Montreal twice from Oct. 22-29. Tampa Bay ended a three-game skid that including an overtime loss at Washington and a home loss to Carolina in Tokarski's first two NHL starts as a replacement for the injured Mathieu Garon (groin).

"We can't blame it on our goalies. They've had our backs so many times this season, and it's one of those games when we had to have their backs and we didn't do that," Bruins defenseman Zdeno Chara said. "It was a tough game for all of us."

Julien agreed with Chara's assessment.

"What's really throwing us off right now is we give those teams leads, and all of a sudden guys are getting frustrated, and we just kind of get away from our game plan," the Boston coach said. "Instead of playing the way we should, we're starting to cheat and we're trying to get those goals back. In frustration, we're making poor decisions and so on and so forth. It just snowballs."

Even though Turco is ineligible for the playoffs because he was signed after the Feb. 27 trade deadline, the Bruins are hoping he can play well enough to help keep the 37-year-old Thomas fresh for the postseason. Before Sunday, Turco hadn't played in a NHL game since a relief appearance for Chicago against Dallas on March 17, 2011.

The 10-year NHL veteran was a backup with the Blackhawks last season. After going unsigned during the summer, he played for EC Red Bull Salzburg in Austria.

Tampa Bay struck quickly against Turco when Ryan Malone's centering pass deflected off Pyatt's right skate and into the net at 1:56. Thompson scored 30 seconds later, and Shannon beat the goalie with a nifty move in front to make it 3-0. Stamkos' second goal was the fourth against Turco, who stopped just eight of 12 shots.

Tokarski was promoted from the minors on March 7 and has been filling in for Garon. Tokarski stopped 29 of 32 shots in his first NHL start at Washington, then played well again in making 22 saves at home in Tampa Bay's 4-2 loss to Carolina on Saturday.

The rookie called his first NHL win, "Pretty unbelievable. A dream come true."

"It's great for him," Boucher said. "It relieves him to get that first win for the team."

Game notes
This was the third of four meetings between the teams this season. The Lightning lead 2-1, winning both games at home. ... Tokarski was credited with an assist on Shannon's goal. ... The Lightning signed forward Vladislav Namestnikov to a three-year, entry level contract. The 19-year-old Namestnikov was the 27th player selected in the 2011 draft. He has been playing this season with the London Knights of the Ontario Hockey League. ... After being outshot 10-2 in the first period, the Bruins held a 32-7 edge the rest of the way.